1. Field of Invention
This invention relates generally to optoelectronic devices and more particularly to protective coatings for optoelectronic devices such as light emitting diodes.
2. Description of Related Art
Optoelectronic devices such as light emitting diodes (LED's), laser diodes, and photo-detectors generally have light transmitting surfaces that are subject to contamination by contaminants present in the environment or in the packaging materials used to package the device. Such contamination may unacceptably degrade the performance of the optoelectronic device over time. Furthermore, semiconductor materials used to fabricate optoelectronic devices, and electrical connections to such devices are typically fragile and should be protected from mechanical shock to make the device structurally sound.
Accordingly, various materials are used to encapsulate optoelectronic devices to protect and isolate the device from environmental effects. Such materials may also be selected to enhance light transmission to or from the device.
Epoxy resins have traditionally been used to encapsulate high-intensity blue or white LED's emitting light in the near ultraviolet spectrum. However epoxy resins suffer from a problem of discoloration and this may result in the LED having a reduced operating lifetime.
Silicone resins have also been used for encapsulating LED's. However discoloration of the silicone resin may still occur even when using silicone resins that are resistant to elevated temperatures and resistant to degradation by the emitted light.
Accordingly there remains a need for improved protective coatings for optoelectronic devices.